the scoop on pest control - cockroaches & silverfish

Cockroaches and silverfish are nocturnal insects that like to hide in dark, warm spaces such as wall cracks and openings around pipes, fitting into gaps as small as one-sixteenth of an inch. Their late-night nature and minute hiding spaces make them hard to detect, and homeowners often only become aware of their presence once they start appearing during the daytime, a sign that populations have grown large. Roaches and silverfish enter homes looking for food and water, feasting on starchy matter like book bindings and wallpaper glue; homeowners frequently find the insects living in stacks of paper and cardboard boxes where starches are ever-present.

The most common cockroaches in U.S. are the German, brownbanded, Oriental and American cockroaches, although the German is the species most often found inside homes. They are all similar in appearance but differ in size, with the American cockroach being the largest of the four. Oriental cockroaches are also referred to as "water bugs" due to their penchant for damp spaces such as basements, leaky pipes and underneath sinks and refrigerators. Wood roaches are another common species, but they prefer moist, outdoor environments. They don't typically invade households because the dry environment isn't conducive to their survival. While most pest-control dusts and sprays will work on common household roaches, wood roaches seem to be impervious to them.

Silverfish, though less repulsive in appearance, are no more welcome in our homes than roaches. These tiny wingless insects can wreak havoc on treasured book collections and stored clothing, and because they can live for up to one year without food and can hide in the tiniest wall crack, silverfish are not easily eliminated.

The proteins found in roach saliva are potent allergens, as are roach feces and body parts. Asthmatics are particularly susceptible to what is called “roach dust,” particles of roach body parts and roach feces, that lingers for a long period of time after roaches have been eliminated. Simply stirring up roach dust by vacuuming or dusting can trigger an asthma attack in some people.

Decaying silverfish bodies and excrement release into the air the allergen tropomyosin, also found in cockroaches and shellfish. This allergen in combination with others found in dust contributes to asthma and rhinitis.

Disease

Roaches may not be sources of disease, but they are known to carry pathogenic bacteria and viruses such as streptococcus and dysentery on their bodies from one place to another, for example, from a sewer to your kitchen table. Additionally, cockroaches can carry diseases like Salmonella, which they get from eating contaminated food and pass in their feces. Silverfish, which do not live off of garbage, are not considered disease bearing.

While cockroaches have never been tied directly to disease outbreaks, scientists suspect they could spur one. In the early 80s, an outbreak of dysentery in a crowded apartment complex in Northern Ireland was thought to have been caused by a large cockroach population living in the building’s sewer system. As the cockroach population came under control, the disease began to disappear. Densely populated living spaces tend to go hand in hand with cockroach populations, and despite a lack of hard evidence tying these pests to disease outbreaks, it’s healthier for your family to keep them at bay.

Hazardous Pesticides

Commercial pest control products for roaches and silverfish are typically comprised of the same chemicals: chlorpyrifos (which has been banned for indoor residential use), propoxur and pyrethrins. But roach pesticides can also include abamectin, hydramethylnon, sulfuramid, hydroprene and fenoxycarb.

Chlorpyrifos (brand name Dursban) is an organophosphate chemical used in liquid sprays and baits. While the Environmental Protection Agency (EPA) has phased out indoor residential use of organophosphates, these can pose indoor air quality threats if sprayed on areas outside your home where they can waft inside. The health effects of chlorpyrifos are severe. Acute health effects include numbness, tingling sensations, incoordination, headache, dizziness, tremor, nausea, abdominal cramps, sweating, blurred vision, difficulty breathing or respiratory depression, and slow heartbeat. Chronic exposure can damage the central nervous, cardiovascular and respiratory systems depending on the length and duration of the exposure. Also, children born to mothers subjected to chlorpyrifos have lower birth weights, linked to developmental problems, and smaller head circumferences, according to a study published in the May 2004 issue of Environmental Health Perspectives.

Chlorpyrifos, though banned, could still be lingering in older pesticides you have stored in your basement or garage. Always read labels, and throw away older pesticides; better yet, buy only the amount you need so storing pesticides is never a concern.

Marketed under the brand name Baygon, propoxur belongs to a class of chemicals called carbamates, and it is the most commonly found carbamate used in silverfish- and roach-control products. Carbamates were introduced in 1951 after roaches began to develop a resistance to organophosphates and chlorinated hydrocarbons (Chlorinated hydrocarbons, which include DDT, were banned by the EPA during the 70s and 80s). Yet roaches are developing a resistance to this class of chemicals as well, making their environmental and health threats even more needless. Carbamates have been linked to fetal death, hormonal changes, DNA damage, birth defects and abnormal sperm, ovaries and eggs. One carbamate, bendiocarb, was phased out by the EPA in 2001 because of its acute environmental and health risks. Futhermore, a study published in January 2006 in the journal Occupational and Environmental Medicine showed that the risk of developing acute leukemia was almost twice as likely in children whose mothers used insecticides in the home while pregnant and long after the birth. In the study, carbamates were found to have been the most commonly used pesticides.

Pyrethrum, an extract derived from chrysanthemum flowers, contains a naturally occurring class of chemicals called pyrethrins that, when administered in small doses, act as a low-toxicity insecticide. However, skin contact with large amounts can cause problems ranging from numbness and itching to stinging, tingling or a feeling of warmth. If ingested, they could cause dizziness, headaches and nausea. Of greater concern are pyrethroids, manufactured chemicals designed as enhanced pyrethrins. Pyrethroids are more concentrated and toxic to both insects and humans in any dosage. Their human health effects are likewise more dangerous, posing risks to neurological function and causing brain abnormalities.

Hydramethylnon is used for roach control in the form of baits and gels. The EPA listed it as a possible human carcinogen and reproductive toxin.

Two other roach pesticides, hydroprene and fenoxycarb, belong to a class of synthetic biochemicals known as insect growth regulators (IGRs), which attack the reproductive system of roaches preventing them from multiplying. IGRs are among the least toxic synthetic pesticides that are available commercially, but few studies exist attesting to their health effects. These tend to take much longer to become effective, and while they’re not considered toxic to people, fish or other wildlife, they are believed to cause allergic reactions in sensitive people.

Environmental

The environmental effects of chlorpyrifos include high toxicity in birds, wildlife and honeybees as well as a long half-life, which means that it persists in soil for an unhealthy amount of time, up to a year in some cases. It also accumulates in fish, causing similar health effects to those in humans, primarily affecting the central nervous system of many aquatic creatures.

Propoxur is toxic to various species of birds, like Canadian geese, and to honeybees. Because it is very soluble in water and does not bind well to soil particles, propoxur has a high potential for groundwater contamination. Additionally, it can enter the roots of a plant and travel to the leaves, where it then poisons insects that feed on the leaves.

Both pyrethrins and pyrethroids are highly toxic to fish, tadpoles, lizards and beneficial insects. When pyrethroids are sprayed, they build up on top of soil. Pyrethrins usually break down over a span of days, but while pyrethroids are supposed to break down under exposure to sunlight, because of the added synthetic chemicals, they can sometimes take months to fully dissolve, posing a greater threat in runoff when sprayed around house perimeters. Compounding the problem is the fact that some lawn-care companies are now adding pyrethroids to fertilizers to kill bugs and feed lawns, resulting in higher concentrations of pyrethroids and pyrethrins that wind up in lakes and streams.

Abamectin, used in a number of roach baits, is an insecticide that attacks the nervous system and paralyzes its prey. Though it breaks down quickly in the environment, abamectin is highly toxic to fish and bees. Hydramethylnon is also toxic to aquatic life.

The chemical sulfuramid, which is used in Raid Max and Raid Roach Baits, poses little potential for harm to humans, although this chemical is highly toxic to birds and aquatic life, specifically rainbow trout.

Boric acid, borax, silica gel and diatomaceous earth are all effective least-toxic pesticides against roaches and silverfish. Diatomaceous earth (DE) is a mixture of ground up diatoms from fossils or lake bottoms, which can be used to combat roaches and silverfish as it robs them of moisture and breaks apart their skin. Unless directly inhaled, it doesn't pose a threat to humans, but keep away from children and pets. DE is most easily applied with a duster, and because roaches like hiding in cracks and very small gaps, these should be sprayed with DE and then sealed to prevent roaches from coming out, as DE can take up to 2 weeks to become effective.

Silica gel is a silicon dioxide substance made from sand, and its absorptive properties allow it to absorb up to seven times its weight in water. The little packets inserted in shoeboxes and handbags contain silica gel, so if you save them, you have a free least-toxic deterrent for silverfish. Because it’s often used to dry flowers, silica gel is available at most art supply and craft stores. It’s most effective in dust form when used to fill cracks in walls or foundations. Silica gel won’t harm humans or animals through skin contact, but it can cause lung damage if inhaled, so use a mask when applying.

The use of roach pheromones in least-toxic pest control is becoming increasingly widespread. Pheromone traps are usually saturated with species-specific pheromones that lure them into a glue-based trap where they get stuck. No pesticides are used, and pheromones have no impact on humans. Because the traps are designed so that only roaches can enter, there’s no risk of inhumanely killing other pests, such as mice, that can get stuck. (For humane methods of killing rodents, see our Pest Control—Rodents Product Report). Pheromone traps, while effective, work best when used in conjunction with other methods of pest control, such as DE or boric acid baits (see below).

Through an integrative pest management (IPM) approach, however, you can prevent infestations from going beyond your control and avoid having to use traps until absolutely necessary.

IPM: Roaches

Roaches come into your house looking for food and water, so deprive them of it as much as possible. If they can’t find it, they’ll usually starve or they’ll be tempted to eat poisonous baits, which you can make yourself (see below).

First, focus on sanitation. Keep food in tightly sealed containers, and keep pet dishes off the floor at night. Never leave your dishes undone, and buy a garbage can with a tightly sealed lid. Roaches love moisture, so check regularly for drips around pipes and plumbing fixtures, and fix leaks as soon as they arise. Check for moisture around refrigerators and houseplants. They also love paper and dark spaces, so keep your house free of stacks of old newspapers and magazines, cardboard boxes and used grocery bags.

Vacuuming your kitchen will help eliminate roaches and their eggs, but if someone in your family is asthmatic, make sure they’re out of the house while the vacuuming takes place to prevent their exposure to stirred-up roach dust. If you’re using a vacuum cleaner with bags, use a bag that’s already half full. An empty bag lets too much dust out. It also may help to clog the bag with flour or cornstarch when you put in a new bag; pour a cup of flour or cornstarch on the floor and vacuum it up.

If you’re not sure why or how roaches are entering your house, sprinkle some talcum powder along your baseboards at night and look for roach tracks the following morning. Once you determine their entry point, seal the cracks in the foundation or baseboards through which they might be entering. When choosing caulk, look for no- or low-VOC varieties; the U.S. Green Building Council recommends Quick Shield VOC-Free Sealant (www.geocelusa.com) or Nail Power Heavy Duty or Latex Repair low-VOC caulks (www.osisealants.com). This is especially helpful in preventing wood roaches from entering the home.

Before caulking, treat the cracks with boric acid powder or diatomaceous earth (see “Shopping Suggestions”). Also, sprinkle a mixture of borax and sugar along their trail. The roaches will eat it, return to their nest and die. Sprinkling Epsom salt along the trail will deter roaches from returning. If you find that roaches are entering through pipes or vents leading in from the outside, cover them with wire screens, which can be purchased at your local hardware store and customized to fit your vents.

Epsom salt, if eaten, is also toxic to roaches. For an easy, no-chemical bait, fill a small bowl with Epsom salts and place wooden strips up to the bowl for easy roach access. The magnesium in the Epsom salts will upset the biological system of a roach and prevent feeding, and the roach will die.

Here’s another easy-to-make recipe for roach bait, but be sure to keep this out of the way of children and pets.

These bugs like humidity—they prefer levels of 75 to 95 percent—so if you find that your books and other important papers are being eaten by silverfish, get a dehumidifier to help lower the humidity in the room. Look for other ways of reducing humidity as well, such as fixing leaks and maintaining pipes. Get rid of old, unwanted stacks of newspapers, magazines, books and fabrics. If you find that your bookshelves are infested with silverfish, remove all books and vacuum both the shelves and the books. Packets of silica gel can be placed on shelves to help lower humidity. Due to their susceptibility to extreme temperatures, silverfish in books can be killed by placing the book in the microwave for 30 to 60 seconds. With the exception of older, more fragile books, most books can undergo microwave radiation without severe damage, although it may soften the glue in paperback books temporarily. Don’t, however, microwave books with gilded edges or those decorated with metallic paint, as that will cause your microwave to spark and potentially cause a fire.

To prevent food products from becoming infested, make sure that you store flour, sugar and cereals in airtight containers. If silverfish find their way into containers anyway, putting the individual containers in the freezer overnight will kill all stages of life. The following morning, empty the contents of the containers into a garbage bag, seal the bag tightly and discard it.

An easy silverfish trap can be made from a glass jar covered with masking tape. Wrap the glass jar entirely with masking tape, and bait the jar with wheat flour or a piece of bread. Place it wherever you see evidence of silverfish. The silverfish will climb up, drop inside and be unable to get out because they can’t crawl up smooth surfaces.

What to look out for

Read labels carefully. Avoid DE and silica gel products that contain additional chemicals like pyrethroids. Related to pyrethroids is a large list of chemicals mostly ending in "thrin," such as deltamethrin and tetramethrin, but a few harmful pyrethroids lack that identifying suffix, including a commonly used outdoor chemical called esfenvalerate that is often mixed with carbamate pesticides. Avoid all of these. Note also that a product may be listed as "natural" because it contains pyrethrum (from the chrysanthemum plant) but may also contain pyrethroids.

Also, avoid products that don't provide a full listing of ingredients on their labels. The EPA requires products to list the active ingredient, but it does not require the listing of inert ingredients which are frequently more hazardous than the active ingredient. Inerts, which enhance the effectiveness of a pesticide, include solvents, surfactants, diluents, carriers, catalysts, synergists and intensifiers, among more than 30 other functions. Manufacturers are not obligated to name the inert ingredients in a product nor are they required to provide any health information about them unless a chemical has already been classified as hazardous by the Occupational Safety and Health Administration.

If you use a DE or silica gel product, keep in mind that they do absorb a certain amount of moisture from the air, so they will need to be reapplied every few months, depending on local climate conditions and the humidity of your home.

Shopping Suggestions

It’s important to note that these products are most effective when used in conjunction with others.

Concern Diatomaceous Earth Crawling Insect Killer
Planet Natural (www.planetnatural.com, 800-289-6656)
Works indoors and out. Insects die within 48 hours of contact. Can be used to apply in cracks and crevices.

* For a good all-purpose insecticide, mix one teaspoon each of eucalyptus and pennyroyal essential oils and two cups of water in a spray bottle. Spray your baseboards and any other areas of infestation.

* Catnip essential oil is another natural deterrent for many insects. Sprinkle drops of the oil on cotton balls and place them in areas where cockroaches travel.

* Mix two ounces of Dr. Bronner’s Peppermint Soap with a gallon of water to make an easy roach repellant.